i think TH has one in one of his future-classic diy-synth books, but does anybody know of another?

the only thing i found was this - what the heck is going here? i know a cmos-switch is being used to choose the output, but i just want to use the waveshaper. how do i do that while omitting the 4066? i can't wrap my head around what's happening here:

look at the aries VCO and/or the Moog Sonic VI schematics for some hints- you just gotta invert one half of the triangle at the right time and add some offset to connect the 2 pieces together- unless you want a double frequency sawtooth.

oh oops! sorry, the Aries ain't what i was thinkin about. that's not even what you need. anyway here is the part[s] of the Sonic VI circuit to look at- switch the FET in time with your comparators output, add in some offset to 'connect' the saw pieces.

in the schematic here, the 30K resistor i circled should be going to V+, this value here (used with the other values) may or may not be right on th money- you can just put a trimmer there, and/or a switch, if you want, a sawtooth with some octave-action sounds pretty good actually.

I'm really curious how the SN-Voice will sound like with this Saw-waveshaper.

probably just like any other sawtooth hehe

yeah i have labeled some of my own equipment with DYMO labels- never real happy with the look.

the building i work in is, apparently, according to several somewhat reliable sources, the building that the very first punch out-stick-on embossing label factory operated- this could be a rumour, of course, but there is evidence all over. Reaaally old labels stuck in the darndest places (still stuck!) with realy nice old fonts. wish i had an old labeler.

I've photoshopped the diagram down to the ramp shaper bit. The Aries one is way complex - and I'd like to know just what U8 'Exponential Converter' actually is.

I think it's fairly clear now: the square wave from the oscillator is operating the 1/4 4066 switch, which changes the polarity and offset of the triangle wave at the output of the op amp, so that it is it's normal self for half the ramp, then inverted and with an offset added for the second half. If you try it, and the output looks weird, then your square wave may need inverting. You should be able to use a FET switch instead of wasting 3/4 of a 4066.

The circuit below using the CA3046 is the sine shaper.

The bottom section is a wave selector and optical amplitude modulator. The clever stuff with the 4066 there allows you to select 1 of 3 waveforms with a normal centre off, single pole toggle, which also helps keep crosstalk down by not routing actual waves to the front panel. Another very neat trick from Mr Bergfors!

TheProf - thanks that helps so much! The mechanics of the 4066 switching made sense in terms of the waveform selection, but your explanation of how it's also used to process the triangle makes perfect sense.

That said, also requiring a pulse wave output is a bit limiting since the SN-Voice only has 1) a triangle output and 2) a Pulse OR Noise output. (I guess there's no getting around that a tri-to-saw converter also requires a pulse for the comparator)

So... if I want to use the saw, I have to switch the SN to Pulse only and forgo all of the cool noise modulation possibilities. For example, yesterday I was using the triangle output as the main signal and using a mixture of the pulse and noise output on the exponential FM input.

This doesn't seem that exciting, but the digital noise can create some fantastic rhythmic sequences when clocked very low.

It might be possible to do a little trickery with a couple of comparators and a set/reset bistable to generate the square wave from the triangle, though this will add a bit of glitchiness to the switching.

logic flow would be like this:

'high' comparator set to just before peak voltage of triangle
'low' comparator set to just before minimum voltage of triangle

On first trip of high comparator, SET the flip flop
On first trip of low comparator, RESET the flip flop

Somewhere there is a trick, I think, for using 2 switches from a 4066 as a set/reset flip flop, but I can't seem to find it just now._________________Mike

what is the relationship between the pulse and the triangle? for this circuit to yield a sawtooth you need a square that changes states when the triangle does, like the prof was talking about.. though that sounds rather a complex circuit to use here.

hmmmmmmmmmmm....
what is the relationship between the pulse and the triangle? for this circuit to yield a sawtooth you need a square that changes states when the triangle does, like the prof was talking about.. though that sounds rather a complex circuit to use here.

josh

Hey Josh,

You're right. The tri to saw shaper needs a square that changes states when the triangle "reverses" at its peaks. This is very tricky to do with comparators because you need to adjust the trip threshold as close as possible to the peaks of the tri. If the tri changes amplitude even a little it can mess you up. Still might be worth trying, but I don't think it'll be easy to get a "perfect" saw. One thought though: the shape of the saw is dependant on the phase relationship between the tri and the square. Because of this, you might actually come up with some "incorrect" results by changing the phase and width of the square. You'll get multiple peaks, or waves that sound just like a triangle, but are offset in strange ways around 0 (two positive peaks followed by two negative peaks, stuff like that). Might even sound neat or make a very interesting LFO, although you never know until you try. Still, you would have an animated wave that is easily voltage-controlled, so I'd think it might just be worth a shot.

page 5 has the waveshaper for this. triangle and square to create pulse, sine and saw. you can skip the first amp the square hits and run a pulse directly into the FET. this might get you what you're looking for. it eliminates the PWM, I think, but if you've got that somewhere else anyway, it works. mine's still a little glitchy every other wave, but it's getting there. I've had to change a few values to get it working and I'd be happy to pass those along if anyone is interested.

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